Splittable chargeable fiber, split multicomponent fiber, a split multicomponent fiber with a durable charge, nonwoven fabric, filter, and yarn containing, and manufacturing processes therefor

ABSTRACT

A process for forming a splittable fiber having the steps of providing a multicomponent fiber; or a multicomponent staple fiber, providing a finish material, and at least partially coating the multicomponent fiber with the finish material to form a splittable fiber. The multicomponent fiber; or a multicomponent staple fiber, contains a first thermoplastic segment comprising polymer component A and a second thermoplastic segment comprising polymer component B. The finish material has an evaporation point of less than about 160° C. A process for forming a nonwoven fabric, a split multicomponent fiber, a split multicomponent fiber with a durable charge, a nonwoven fabric, and a filter and/or a spun yarn formed by the fibers herein is also described.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.63/120,720 filed Dec. 2, 2020, the disclosure of which is incorporatedby reference in its entirety.

FIELD OF THE INVENTION

The current invention relates to the field of splittable fibers andmanufacturing processes therefor. More particularly the currentinvention relates to the field of splittable fibers formed of amulticomponent staple fiber and manufacturing processes therefor.

BACKGROUND OF THE INVENTION

Artificial fibers are typically spun, drawn, and textured prior to beingspun into a yarn. Often such artificial fibers are textured by crimpingprior to use as crimping provides benefits such as processability(carding in particular), improved skin feel, softness, stretch,fluffiness, etc. to the fibers. The fibers may be selected for variousproperties, such as chemical resistance, fluffiness, surface area,hydrophobicity/hydrophilicity, etc.

Carded fibers are known for use in filtration media and other uses, viamechanical filtration principles such as diffusion, interception,inertial impaction and sieving to capture and retain particles ofvarious sizes. Splittable fibers having an increased surface area arealso known for use in filtration media, leading to a reduced pore sizewith the same amount of material which leads to higher filtrationefficiency in the Z direction of the filter media.

Splittable fibers are known in the art to produce sub-fibers which havean increased surface area, and therefore different properties than theoriginal (single-strand) splittable fiber itself. Such splittable fibersare typically produced from a multicomponent fiber which is then splitinto multiple sub-fibers. The multicomponent fibers are known to containmixtures of polymers, a charge-enhancing additive, a filler, a finishmaterial, etc. to create the splittable fiber. See, e.g., U.S. Pat. No.5,336,552 by Strack, et al., to Kimberly-Clark Corp., granted on Aug. 9,1994; U.S. Pat. No. 5,382,400 to Pike, et al., to Kimberly-Clark Corp.,granted on Jan. 17, 1995; US 2003/0203695 A1 by Polanco, et al., toKimberly Clark Worldwide Inc., published on Oct. 30, 2003, all of whichare hereby incorporated by reference in their entireties. Finishmaterials are known to be added to splittable fibers to reduce thefriction and heat generated during further processing, such as during acarding process. Finish materials are also employed to prevent staticelectricity from building up on the fibers during such furtherprocessing.

Such splittable fibers and corresponding processes are known to producefibers which have a significantly larger surface are when split intosub-fibers. Either before or after splitting, these fibers may be thenformed into, for example, filters, filter materials, nonwovenfabrics/materials, etc. Such splittable fibers are especially useful infilters, filter materials, etc. where the splittability of the fiberscan significantly increase filtration efficiency. Similarly, higherwater pressure during hydroentanglement may lead to higher splitting,but may conversely also create “large” apertures throughout the nonwovenfabric which then in turn decreases the filtration efficiency.Furthermore; traditional hydroentanglement equipment is large, employinghigh pressure water with many required safety features; these machinesare therefore very expensive to purchase and install, and yet often suchhigh energy/high impact processes are typically required in order tosignificantly split the current splittable fibers used in nonwovenfabrics into their component sub-fibers.

Relatively gentle processes such as carding and needle punching will not(significantly) split current splittable fibers, because they lack thephysical force necessary to significantly split current splittablefibers.

Additional methods of increasing filtration efficiency are also known,such as electret charging of fibers. However, it has been found thatcurrent splittable fibers are difficult to charge and/or quickly losewhatever charge they acquire. Typically, current splittable fibers aremulticomponent fibers that are split during a hydroentanglement process.As a hydroentanglement process is a very energetic process the waterjets impart sufficient kinetic energy to break the multi componentfibers into sub-fibers. However such hydroentangled nonwoven fabricssuffer from specific drawbacks as the hydroentanglement process itselfcauses large holes/pores in the nonwoven fabric which decreases thepotential filtration efficiency. Also, such nonwoven fabrics, and thesplit fibers therein, are typically not chargeable, and certainly arenot capable of holding a durable charge, which also reduces theirpotential filtration efficiency. Accordingly, the filtration efficiencyof current splittable fibers is limited by their lack ofcharge/chargeability. See, for example, US 2015/0343455 A1 by Schultz,et al., to 3M Innovative Properties Co., published on Dec. 3, 2015,hereby incorporated by reference in its entirety.

Next Nano (nxtnano.com; Claremore, Okla., USA) nano fiber-based filtermedia are formed by depositing fine fibers onto the surface of apleatable support layer making a physical filtration structure thatrelies upon sieving only. The fibers are very sensitive and it isdifficult to get them to adhere to the surface of the support layer. Thefibers act as a high surface area membrane would, by basically surfaceloading contaminant particles. As soon as the surface blinds off orbuilds a “dirt cake” the resistance increases to maximum and the filtermedia has difficulty maintaining airflow. Furthermore, such nanofiber-based filters are known to typically cost up twice what otherfilters cost.

Conversely, structures that rely only on a high charge potential such as“Tribo electret media” are designed to be of very low air resistance buthave a very powerful surface charge. The advantage from this type ofmedia is that they “depth load” particulates and possess a long lifewith only a small increase of resistance over many weeks or even months.However, if a filter made with this fibers ingests an oily smoke fromcigarettes or forest fires, the charge is quickly masked, and the filterrapidly loses efficiency. These filters have been misapplied and placedin commercial buildings where the filters prematurely fail due to theloss of charge when the building ventilation system becomes contaminatedwith cigarette smoke. The EU has recognized this mis-application and hasinitiated the new ISO 16890 standard, hereby incorporated by referencein its entirety, where the filter is given a rating by averaging thebeginning efficiency, discharging the media and retesting. The resultsare quite dramatic for a media like Tribo electret where it may have aninitial efficiency of MERV 13 but after discharging may end up with aMERV 6.

However, it has been found that as the finish materials currently usedare intended to reduce static, build up in the nonwoven fabric, theyalso may cause the splittable fiber to quickly lose the charge after,for example, electret charging via corona processing. Thus, currentsplittable fibers are not known to be charged, or to durably carry anelectret charge. This in turn has been now found to limit theirfiltration efficiency. Accordingly, there exists a need for a finishmaterial for splittable fibers which does not cause the splittable fiberto lose charge.

Accordingly, there exists a need for a splittable chargeable fibercapable of holding a durable charge, especially for the production offiltration media, a nonwoven fabric made therefrom, and processes forforming such a splittable chargeable fiber and nonwoven fabric. Therealso exists the need for a process to manufacture a splittablechargeable fiber capable of holding a durable charge. There also existsa need for a filtration product which possesses the advantages of a nanofiber-based filter and a charged filter to provide efficient and lastingfiltration.

SUMMARY OF THE INVENTION

An embodiment herein relates to a process for forming a splittable fiberhaving the steps of providing a multi component fiber; or amulticomponent staple fiber, providing a finish material, and at leastpartially coating the multicomponent fiber with the finish material toform a splittable fiber. The multicomponent fiber; or a multicomponentstaple fiber, contains a first thermoplastic segment comprising polymercomponent A and a second thermoplastic segment comprising polymercomponent B. The finish material has an evaporation point of less thanabout 160° C.

An embodiment of the present invention relates to a process for forminga nonwoven fabric having the steps of providing a splittable fiber byproviding a multicomponent fiber; or a multicomponent staple fiber asdescribed herein, and forming the splittable fiber into a nonwovenfabric.

An embodiment of the present invention relates to a split multicomponentfiber comprising a durable charge.

An embodiment of the present invention relates to a nonwoven fabric, afilter and/or a spun yarn formed by the fibers and processes describedherein.

Without intending to be limited by theory, it is believed that thepresent invention may provide a splittable fiber which is capable ofreceiving and maintaining/holding a durable charge. This splittablefiber may then be further formed into, for example, a filtration mediapossessing significant advantages over existing filtration media.

Without intending to be limited by theory, it is also believed that thepresent invention may provide surprising benefits by combining the bestadvantages of nano fiber-based filters and electret-charged filters byincorporating high surface area physical filtration and electret chargeto enhance fine particle retention. The present invention is believed toprovide both depth load filtration and to maintain long-lastingperformance with little or no resistance spikes. It is believed that thepresent invention significantly reduces the chances of prematurelyfailure due to, for example, cigarette smoke, while also providingsignificant manufacturing and cost advantages. The invention herein mayprovide one or more benefits such as improved filter loading, improvedfilter life, improved MERV rating, improved resilience/scuff resistance,etc.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a shows a cross-sectional views of an embodiment of a splittablemulticomponent fiber;

FIG. 1b shows a cross-sectional views of an embodiment of a splittablemulticomponent fiber;

FIG. 1c shows a cross-sectional views of an embodiment of a splittablemulti component fiber;

FIG. 2 shows a partial side view of an embodiment of a splittable fiberof the present invention after splitting;

FIG. 3 shows a partial side view of an embodiment of a splittable fiberof the present invention after splitting; and

FIG. 4 shows a cross-sectional view of a hollow multicomponent fibercontaining a plurality of alternating thermoplastic segments.

The figures herein are for illustrative purposes only and are notnecessarily drawn to scale.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Unless otherwise specifically provided, all tests herein are conductedat standard conditions which include a room and testing temperature of25° C., sea level (1 atm.) pressure, pH 7, and all measurements are madein metric units. Furthermore, all percentages, ratios, etc. herein areby weight, unless specifically indicated otherwise. It is understoodthat unless otherwise specifically noted, the materials, compounds,chemicals, etc. described herein are typically commodity items and/orindustry-standard items available from a variety of suppliers worldwide.

As used herein, the terms “a”, “an”, and “the” are interchangeable with“at least one” to mean one or more of the elements as described.

As used herein, the term “durable charge” indicates an electret chargethat retains at least 90% of the original charge after at least about 1year; or at least about 2 years; or at least about 3 years, in normalconditions of packaging, storage and handling. A simple hand held staticmeasuring device can be used to measure the initial charge afterelectret charging, and the retained charge after the above period oftime, and the percentage retention is easily calculated.

As used herein, “electret” refers to a material that exhibits aquasi-permanent electric charge.

As used herein the phrase “multicomponent fiber” indicates a fiber thathas been formed from a plurality of component polymers, or the samepolymer having different properties and/or additives, and extruded asseparate sub-fibers (i.e., strands) from separate extruders. Typicallythe multi component fiber will be made from a plurality of differentcomponent copolymers; or each sub-fiber is made from a different polymerfrom that of the adjacent sub-fiber(s). The sub-fibers are then combinedto form a single fiber, for example, by spinning. Typically thesub-fibers are arranged in consistently-positioned positions across thecross-section of the multicomponent fiber. The relative positions of thesub-fibers may be in, for example, pie-wedges such as seen in FIGS.1a-1c , stripes, etc. as known in the art. See, for example, U.S. Pat.No. 5,108,820 to Kaneko, et al., assigned to Mitsubishi PetrochemicalIndustries, granted on Apr. 28, 1992, hereby incorporated herein byreference in its entirety.

As used herein the term “nonsplittable fiber” indicates a fiber having asingle, relatively fixed and constant denier along substantially itsentire length even after processing, including, for example, carding,hydroentanglement, etc., into a nonwoven web. In an embodiment herein,the nonsplittable fiber is a fiber having a roughly circularcross-sectional shape in which the entire fiber surface comprises asingle polymer to a depth of at least 10% of the fiber's maximum radius;or for a non-circular cross sectional fiber, such as a trilobal fiber,wherein a single polymer comprises substantially the entire fibersurface.

As used herein “splittable fiber” indicates that a multi component fiberhaving a given width and cross-sectional configuration may be changedafter fiber extrusion; substantially as part of the nonwoven fabricformation process, typically through physical disruption of theattachment between individual sub-fibers by the application ofmechanical energy. Typically, a splittable fiber herein will split intoat least 2 sub-fibers for about 20% or more; or for about 30% or more ofits length; or for about 40% or more of its length after a typicalcarding process having a main cylinder:worker roll speed ratio of 20:1;or 15:1; or 10:1 at a given output speed.

As used herein the term “staple fiber” indicates a fiber; typically anextruded fiber, which may be from about 1.25 cm to about 16 cm in lengthtypically; due to cutting. Staple fibers are typically then formed intoa nonwoven fabric via one or more forming processes such as carding, airlaying, adhesive bonding, thermal bonding, etc.

An embodiment of the present invention relates to a process for forminga splittable fiber having the steps of providing a multicomponent fiber;or a multicomponent staple fiber, providing a finish material, and atlast partially coating the multicomponent fiber, or the multicomponentstaple fiber, with the finish material. The multicomponent staple fibercontains a first thermoplastic segment containing polymer component A,and a second thermoplastic segment containing polymer component B. Thefinish material has an evaporation point of less than 160° C.

The polymer component A and polymer component B are typically usefulherein when a carded web made from a pie wedge fiber made from thepolymer pair is observed to contain at least 20% of the pie wedge fibersthat have split to any degree after carding. This typically means thatpolymer component A and polymer component B have different empiricalchemical formulas. Without intending to be limited by theory, it isbelieved that, for example, two different grades of polypropylene withdifferent molecular weights would have the same empirical chemicalformula and would not be sufficiently different for 20% or more of thepie wedge fibers to split during carding. Similarly, it is believed thata polyethylene terephthalate (PET) and an isophthalic acid/terephthalicacid coPET would have identical empirical chemical formulas (but notidentical chemical structures) and would thus it would be unlikely for20% or more of the pie wedge fibers to split during carding. Incontrast, for example, PET and polypropylene have different chemicalformulas and are sufficiently different so as to function in theinvention. Thus, without intending to be limited by theory; it isbelieved that the present invention is operable and may provide asplittable fiber so long as the empirical chemical formula of polymercomponent A is significantly different from; or different from; polymercomponent B.

The multicomponent fiber; or multicomponent staple fiber, useful hereinis a fiber having a plurality of thermoplastic segments; typically afirst thermoplastic segment and a second thermoplastic segment, althoughadditional thermoplastic segments may also be included, such as a thirdthermoplastic segment, a fourth thermoplastic segment, etc. Themulticomponent fiber typically contains at least 4 distinctthermoplastic segments; or from about 4 to about 128 distinctthermoplastic segments; or from about 8 to about 64 distinctthermoplastic segments; or from about 16 to about 32 distinctthermoplastic segments. Each thermoplastic segment may be formed ofpolymer component A or polymer component B as desired, as long as atleast one thermoplastic segment in the multicomponent fiber is formed ofpolymer component A, and at least one thermoplastic segment in themulticomponent fiber is formed of polymer component B. Typically, inorder to promote the desired splitting of the multicomponent fiber intothe desired sub-fibers, each segment will be of a different polymer thanthe adjacent segment(s).

It is further understood that in a multicomponent fiber, thethermoplastic segments are typically arranged in the fiber such thatthey define a specific spatial arrangement within the fiber's crosssection. Furthermore, this specific spatial arrangement typically doesnot vary significantly along the entire length of the multicomponentfiber prior to splitting. See, for example, embodiments of themulticomponent fiber herein containing multiple thermoplastic segmentsin FIGS. 1a-1c , showing cross-sectional views of various multicomponentfiber embodiments, where the multicomponent fiber, 10, contains aplurality of thermoplastic segments, 12, 12 a, 12 b, 12 c, 12 d, etc.each of which may correspond to a sub-fiber (see FIG. 2 at 14). Thevarious thermoplastic segments are typically coextruded together to forma single multi component fiber, although they may be separately extrudedand then combined, typically quickly combined (before the individualthermoplastic segments harden), to form the multicomponent fiber. Eachthermoplastic segment has the potential to form its own sub-fiber (seeFIG. 2 at 14) upon splitting.

In an embodiment herein, a process for forming a nonwoven fabricincludes the steps of providing a splittable fiber, and forming thesplittable fiber into a nonwoven fabric. The splittable fiber isprovided by providing a multicomponent fiber; or a multicomponent staplefiber, containing a first thermoplastic segment containing a polymercomponent A, and a second thermoplastic segment containing a polymercomponent B, providing a finish material having an evaporation point ofless than 160° C. and at least partially coating the multicomponentstaple fiber with the finish material.

In an embodiment herein, the step of forming the splittable fiber into anonwoven fabric may be, for example, forming step is selected from thegroup consisting; of carding, thermal bonding, needle punching,spunbonding/spinbonding, air laying, hydroentanglement, melt blowing,hydro pulping, refining, wet laying, passing thorough air oven,cross-lapping, and a combination thereof; or thermal bonding, needlepunching, hydropulping, wet-laying, chemical bonding (e.g., for acryliclatex), melt blowing, air laying, carding, needling, hydroentanglement,and a combination thereof; or thermal bonding, needlepunching,hydropulping, wet laying, and a combination thereof. Typically carding,spunbinding/spunbonding, air-laying, melt blowing and melt laying areconsidered processes for initially forming a nonwoven web, while thermalbonding, needle punching, hydroentanglement, chemical bonding, andcross-lapping are processes that consolidate the initially-formednonwoven web into a nonwoven web which is typically possesses increasedstrength, rigidity, etc. as compared to the initially-formed nonwovenweb. Hydro pulping and refining are used prior to wet-laying tocondition the water-borne fibers. Accordingly, as used herein, the term“forming, step” includes all different phases of the physical formingprocess, from the point that fibers are extruded, to the finalproduction of the nonwoven fabric. However, the forming process as usedherein does not necessarily include the electret charging step.

It is understood that when the multicomponent fiber splits apart intosub-fibers, they do so in a distribution of splitting at any specificlocation along the multicomponent fiber (see, e.g., FIG. 2 and FIG. 3).That is, for example, at a certain location, a multicomponent fibercomprising 16 thermoplastic segments may split entirely into 16 separatesub-fibers, with each sub-fiber containing a single thermoplasticsegment. Alternatively a multicomponent fiber (or even the same multicomponent fiber at a different location) may split into 6 sub-fiberseach containing one thermoplastic segment each, 2 sub-fibers comprising2 thermoplastic segments each (not split apart from each other), and onesub-fiber comprising 6 thermoplastic segments that remain adhered toeach other in a single sub-fiber. In other fibers, or even along thesame multicomponent fiber, the distribution of single-segment andmultiple segment sub-fibers may be different.

FIG. 2 shows a partial side view of an embodiment of a splittable fiber,20, of the present invention after splitting. The multicomponent fiber,10, contains 8 different thermoplastic sub-fibers, 12 a-12 h from top tobottom respectively, to form the splittable fiber, 20. At point A-A,along the multicomponent fiber, 10, thermoplastic segments 12 a, 12 b,12 c, 12 d, and 12 e are joined together in a sub-fiber 14 a, whilethermoplastic segments 12 f, 12 g and 12 h are joined together in asub-fiber, 14 b. The split distribution can be measured using, forexample, the BET test, the Micronaire test, SEM analysis, etc. asdescribed herein.

However, at point B-B along the same multicomponent fiber, thermoplasticsegment 12 a has split from thermoplastic segments 12 b and 12 c whichare still joined together. Thermoplastic segment 12 d and thermoplasticsegment 12 e are split as well as single sub-fibers, 14, whilethermoplastic segments 12 f, 12 g, and 12 h are still joined together insub-fiber 14 b.

At point C-C, all of the 8 thermoplastic segments 12, have split apart,so thermoplastic segments 12 a, 12 b, 12 c, 12 d, 12 e, 12 f, 12 g and12 h can all be seen and identified separately as individual sub-fibers.

At point D-D, all of the 8 thermoplastic segments are joined together asa single multicomponent fiber. One skilled in the art understands thatadditional combinations and arrangements of the thermoplastic segmentsto form various sub-fibers are also possible as well, either indifferent multicomponent fibers, or at different places in the samemulticomponent fiber.

Without intending to be limited by theory it is believed that such asplittable fiber having a variable split distribution is useful as itallows the production of various nonwoven fabrics having differentphysical features and properties such as fluffiness, thickness,insulation levels, air/water resistance, filtration levels, etc. fromthe same multicomponent fiber. Furthermore, it is believed that thesplit distribution can be increased by changing the process, forexample, more vigorous carding leads to a higher splitting of thesplittable fibers, both along the same fiber as well as in differentfibers.

FIG. 3 shows a partial side view of an embodiment of a splittable fiberof the present invention after splitting. Specifically, the splittablefiber, 20, can be shown split into thermoplastic segments, 12 a, 12 b,12 c, 12 d, 12 e, 12 f, 12 g, and 12 h, for a majority of its length. Ascan be seen on the right side of the figure, the splittable fiber, 20,is split into thermoplastic segments, 12 a, 12 b, 12 c, 12 d, 12 e, 12f, 12 g, and 12 h, each of which corresponds to a sub-fiber, 14 a, 14 b,14 c, 14 d, 14 e, 14 f, 14 g, and 14 h.

FIG. 4 shows a cross-sectional view of a hollow multicomponent fiber,10, containing a plurality of alternating thermoplastic segments, 12 aand 12 b. Specifically, the multicomponent fiber, 10, contains a hollowcenter, 16. Each segment 12 a is formed of polypropylene and in theembodiment of FIG. 4 each segment 12 b is formed of polymethylpentene,which would normally bind together too strongly to be split when formedinto a shape such as FIG. 1a . However, due to the lower adjoiningsurface area, 18, between the different segments, 12 a and 12 b, due tothe hollow center, 16, in the multicomponent fiber, 10, these segments,12 a and 12 b, may still be split from each other during a cardingprocess. Thus, in an embodiment herein, the multicomponent fiber is ahollow fiber. In an embodiment herein, the polymer component A ispolypropylene and polymer component B is polymethylpentene.

As mentioned above, polymer component A and polymer component B havedifferent empirical chemical formulas. In an embodiment herein, thepolymer component A includes a polymer; or a polymer selected from thegroup consisting of a polyamide, a sulfur-containing polymer, anaromatic polyester, an aliphatic polyester, a polyolefin, and acombination thereof; or a polyamide, a polyphenylene sulfide, apolyarylene terephthalate, a polyarylene isopthalate, a polylactic acid,a poly hydroxyalkanoate an aliphatic polyester, a polypropylene, apolyethylene, a polymethylpentene, and a combination thereof; or nylon,polyphenylene sulfide, polyethylene terephthalate, polylactic acid, polypropylene, and a combination thereof; or PET, polylactic acid polymer,polypropylene, and a combination thereof. As used herein with respect tothe polymers, the term “a combination thereof” specifically includescopolymers, homopolymers, and blends thereof.

In an embodiment herein, the polymer component B includes a polymer; ora polymer selected from the group consisting of a polyamide, asulfur-containing polymer, an aromatic polyester, an aliphaticpolyester, a polyolefin, and a combination thereof; or a polyamide, apolyphenylene sulfide, a polylactic acid, a polyarylene terephthalate, apolyarylene isopthalate, a polyhydroxyalkanoate an aliphatic polyester,a polypropylene, a polyethylene, a polymethylpentene, and a combinationthereof or a nylon, a polyphenylene sulfide, a polylactic acid, apolyethylene terephthalate, a poly propylene, and a combination thereof;or a PET, a polylactic acid polymer, a polypropylene, and a combinationthereof.

In an embodiment herein, the polymer component A and/or the polymercomponent B contains a polyolefin; or a polyolefin selected from thegroup consisting of a polypropylene, a polyethylene, and a combinationthereof. Without intending to be limited by theory, it is believed thatpolyolefins; or polypropylene, polyethylene, and the combination thereofare especially useful for acquiring and holding an electret charge.

In an embodiment herein, the polymer component A contains a polyolefinpolymer, and polymer component B contains a non-polyolefin polymer. Inan embodiment herein, the polymer component A contains a polylactic acidpolymer, and polymer component B contains a non-polylactic acid polymer.

The finish material herein is applied to the surface of the splittablefiber to aid in lubricating the splittable fiber to reduce heatgeneration and to reduce static during further processing, such ascarding, etc. Generally in the art, traditional finish materials containmineral oils or synthetic oils with anti-static additives. Sometimesthese traditional finish materials may contain animal fats, or fattyacids. However, it has now been found that these traditional finishmaterials reduce or eliminate the charge induced or added on to thesplittable fiber, during, for example, electret charging; or electretcharging via corona charging. Accordingly, an embodiment of theinvention herein includes the step of removing the finish material fromthe splittable fiber prior to electret charging; or removing the finishmaterial from the splittable fiber during the electret charging process.In an embodiment herein, the finish material is removed during, forexample, the dwell time in an oven, etc.

A finish mated al may be required for increasing lubrication duringfurther processing, to reduce static charge build up, etc. Thus, in anembodiment herein, the finish material has an evaporation point of lessthan about 160° C.; or from about 30° C. to about 160° C.; or from about40° C. to about 150° C.; or from about 50° C. to about 100° C.

The finish material herein may be a substantially water-soluble; orwater-soluble finish material, which is especially intended to wash awayduring, for example, washing, a hydroentanglement process, etc. In anembodiment herein, the finish material is a water-soluble finishmaterial, and the forming process includes the step of hydroentanglingthe splittable fiber while coated with the finish material.

Without intending to be limited by theory, it has been found that whenthe evaporation temperature is in the range above, then most; orsubstantially all, of the finish material is removed; or evaporated,during the thermal bonding process to form the nonwoven web. In anembodiment herein, the process herein includes the step of removing, byweight, at least a portion; or from about 50% to about 100% of thefinish material; or from about 75% to about 100% of the finish material;or form about 80% to about 100% of the finish material, from thenonwoven fabric; the multi component fiber, and/or the splittable fiber;or from the splittable fiber, during or after the forming step when thesplittable fiber is formed into a nonwoven fabric and prior to theelectret charging process. In an embodiment herein, the nonwoven fabricforming process removes at least a portion of the finish material; orfrom about 50% to about 100% of the finish material; or from about 75%to about 100% of the finish material; or form about 80% to about 100% ofthe finish material; or substantially all of the finish material, byweight from the nonwoven fabric.

In an embodiment herein, the finish material comprises water, alubricant, and an emulsifier. In an embodiment herein, the lubricant isa selected from a plant-based oil, a natural oil, a synthetic oil, awater-soluble lubricant, and a combination thereof; or a vegetable oil;a mineral oil and a combination thereof; or a light vegetable oil, alight mineral oil, and a combination thereof; or a coconut oil; a cornoil, and a combination thereof. It is preferred that the lubricantherein possess a low molecular weight, a high viscosity, and few, or nomolecular byproducts when exposed to heat, and no residue afterevaporation. In an embodiment herein the finishing material and/or thelubricant are compliant with the United. States Federal DrugAdministration guidelines regarding GRAS (Generally Regarded As Safe)list (See, for example,https://www.fda.gov/food/food-ingredients-packaging/generally-recognized-safe-gras;and US Code of Federal Regulations: 21 CFR 177.2800; 21 CFR 176.210; 21CFR 178.3400), all hereby incorporated by reference in its entirety.

In an embodiment herein, the finish material is a water-soluble finishmaterial; typically containing a water-soluble lubricant; or containingsufficient emulsifier to fully emulsify any and all oil in the finishmaterial, or is a fully water-soluble finish material, so that during,for example, a hydroentanglement process, the finish material washesaway; or substantially washes away, from the splittable fiber.

In an embodiment herein, the emulsifier acts as an antistatic compound;or an antistatic compound having an evaporation point of less than about160° C.; or from about 30° C. to about 160° C.; or from about 40° C. toabout 150 CC; or from about 50° C. to about 100° C. In addition, thefinish material may contain a specific antistatic material other thanthe emulsifier.

In an embodiment herein, the finish material may also contain astabilizer, a thickener, a thinner, an anticoagulant, an antimicrobialcompound and a combination thereof. These compounds are well-known inthe art and available from multiple well-known suppliers worldwide.

The multicomponent fiber is at least partially coated; or coated, in acoating step with the finish material to form a splittable fiber. Thecoating step may include, for example, spraying the finish material ontothe multicomponent fiber, immersing the multicomponent staple fiber inthe finish material, contacting the fiber and a film of liquid finishmaterial on the surface of a transfer roll (for example, a kiss-rollapplication process), contacting the fiber with a bead of the finishmaterial as the fiber passes through a grooved applicator (e.g., using ametered-finish application process), and a combination thereof.

In an embodiment herein, where the invention employs a multi componentstaple fiber, the process herein may further include the step of cuttinga multicomponent fiber to form a multicomponent staple fiber, crimping amulticomponent staple fiber to a length of from about 1.25 cm to about16 cm, and a combination thereof.

Once the multicomponent fiber is formed into the splittable fiber, thenthe splittable fiber is typically formed into a nonwoven fabric by, forexample, by the forming processes described herein. Such formingprocesses are known in the art.

In an embodiment herein, the splittable fiber is fully split into aplurality of sub-fibers. In an embodiment herein, the smallestsub-fibers have a linear density of less than about 5 denier; or lessthan about 2 denier; or less than about 1 denier; or less than about 0.8denier; or less than about 0.4 denier.

In an embodiment herein, the nonwoven web includes a nonsplittable fiberhaving a linear density of greater than about 1 denier; or from about1.5 denier to about 4 denier; or from about 1.5 denier to about 3denier. In an embodiment herein, the nonwoven fabric herein furthercontains an additional nonsplittable fiber having a linear density offrom about 1 denier to about 20 denier to provide additional propertiessuch as stiffness, the ability to hold a shape or a crease/fold, etc.

An embodiment of the present invention further includes a splitmulticomponent fiber having a durable charge as described herein.

In an embodiment herein, the nonwoven fabric also contains anonsplittable fiber in addition to the splittable fiber. Thus, in anembodiment of the nonwoven fabric formation process herein, the processincludes the step of providing a nonsplittable fiber. The nonwoven webis then formed from the splittable fiber and the nonsplittable fiber. Inan embodiment herein the nonwoven fabric contains from about 1% to about100%; or from about 3% to about 97%; or from about 5% to about 95%; orfrom about 10% to about 90% splittable fibers by weight of the nonwovenfabric. It is believed that a blend of both splittable fibers andnonsplittable fibers may provide benefits such as strength, shaperetention, filtering, etc. In an embodiment herein, the nonwoven fabriccontains at least 20% nonsplittable fibers, especially if it is thermalbonded during the forming step.

In an embodiment herein the finish material is removed after the formingstep; or after the splittable fiber is split. Without intending to belimited by theory, it is believed that by removing the finish materialfrom the splittable fiber, the nonwoven fabric, the split multicomponentfiber, etc. the resulting individual split multicomponent fiber'sability to acquire and hold a durable charge will not be significantlyabated or reduced by the antistatic properties of the finish material.

In an embodiment herein, the process for forming a nonwoven web includesthe step of splitting the multicomponent fiber; or the multicomponentstaple fiber; or the splittable fiber, into a split fiber. In anembodiment herein, the splitting step includes a needle punchingprocess, a hydroentanglement process, a carding process, a flexingprocess, a twisting process, a stretching process, a drawing process, ascraping process, a crushing process, a rolling process, a hydropulpingprocess, a stitchbonding/stitchbinding process, and a combinationthereof, or a carding process, a needle punching process, a hydropulpingprocess, and a combination thereof. In an embodiment herein thesplitting step is the same as the forming step.

In an embodiment herein, the electret charging process charges athermoplastic component in the splittable fiber, the split fiber, themulticomponent fiber, the multicomponent staple fiber, the nonwovenfabric, and/or etc. selected from the group of the first thermoplasticcomponent, the second thermoplastic component, and a combinationthereof; or the split fiber, the multicomponent fiber, the splitmulticomponent fiber, and/or the nonwoven fabric. In an embodimentherein, the electret charging process useful herein is selected from thegroup of corona charging, ion bombardment, atmospheric plasma deposition(APD), other charging methods, and a combination thereof; or coronacharging, ion bombardment, APD and a combination thereof; or coronacharging, APD, and a combination thereof. Corona charging is known inthe art and has its roots in the foil and film lamination process. Earlyresearch in nonwoven media started in the 1990's when Dr. Peter Tsaifrom University of Tennessee developed and patented a system to enhancemelt blown polypropylene with a similar technology designed to givefilms a normalized surface energy for secondary processing. Dr. Tsaifound that by applying a strong polarity of charge to a polypropylenemelt blown structure that the surface energy attracted, removed and heldfine particles (>1.0 micron) enhancing an otherwise low efficiencyfiltration media.

In an embodiment herein, the electret charging process includes theprocess of API/In an embodiment herein, the electret charging processfirst employs an atmospheric plasma deposition process and subsequentlya corona charging process. Without intending to be limited by theory, ithas been found that in addition to including an electret charge in thefibers, API) may can also remove oligomers and other low molecularweight by-products, such as the finish material, from thermoplasticpolymeric fibers as well as providing a nano-etched finish giving thefibers a more suitable surface. It is further believed that the APDprocess may actually clean and functionalize the fiber surface such thatwhen the API) process is followed by a corona charging process, thecorona charge may be stronger, and/or may last an even longer time;i.e., is even more durable.

In an embodiment herein, the electret charging; or the corona chargingprocess, ion bombardment, the APD process, other charging methods, and acombination thereof; or the heat from the corona charging process, theAPD process, and a combination thereof, helps to remove finish materialfrom the splittable fiber, the nonwoven fabric, the multicomponentfiber, the multicomponent staple fiber, the split fiber, and/orsub-fiber. In an embodiment herein, the electret charging; or the coronacharging, imparts a negative charge to the outer surface of thesplittable fiber, the nonwoven fabric, the split fiber, themulticomponent fiber, the multicomponent, staple fiber, and/orsub-fiber. Without intending to be limited by theory, it is believedthat this negative surface energy on the outer surface of the splittablefiber, the nonwoven fabric, the split fiber therefore attractspositively-charged particles from the air or other media passing throughthe filter, thereby significantly increasing filtration efficacy. Theelectret charging may impart either a net negative charge or a netpositive charge on the nonwoven fabric, the multicomponent fiber,multicomponent staple fiber, and/or the split fiber. An electric chargeallows the nonwoven fabric, the multicomponent fiber, the multicomponentstaple fiber, and/or the split fiber to attract oppositely-chargedparticles when being used as, for example, a filtration matrix.

In an embodiment herein, a charge-enhancing additive added is includedinto the multicomponent fiber; or the polymer component A; or thepolymer component B. The charge-enhancing additive enhances thedevelopment and/or retention of an electret charge; or a staticelectrical charge. In an embodiment herein, the charge-enhancingadditive is selected from the group of stearate salts; phosphate metalsalts, benzoic acid salts, zinc, and a combination thereof; or thecharge-enhancing additive is selected from the group of calciumstearate, magnesium stearate, sodium phosphate, sodium benzoate, zincsalts, and a combination thereof; or the charge-enhancing additive isselected from the group of calcium stearate; magnesium stearate, sodiumphosphate, and a combination thereof. Without intending to be limited bytheory, it is believed that stearate salts; or calcium stearate andmagnesium stearate particles; or calcium stearate particles having adiameter of 5 microns (μ) or less and magnesium stearate particleshaving a diameter of 5μ or less are especially desirable if themulticomponent fiber and/or a sub-fiber contains polypropylene. Withoutintending to be limited by theory it is believed that once themulticomponent fiber and/or the sub-fiber contains and/or is coated withthe charge-enhancing additive(s), the charge-enhancing additive(s) mayform a capacitor-like structure which may enhance the electret chargedensity and/or durability as compared to when no charge-enhancingadditive is present.

In an embodiment herein, the charge-enhancing additive is an organicacid metal salt composed of at least a C₁₀ carbon-chain organic acid anda metal ion work function of 4 eV or more. Examples of the organic aciduseful herein include C₁₀ or higher carbon chain length carboxylicacids, organic phosphoric acids, organic sulfonic acids, and the like,especially lauric acid, linolenic acid, t-butylbenzoic acid,di-(t-butylphenyl) phosphoric acid, and/or stearic acid. The metal saltions useful herein include, for example, aluminum ions, iron ions,nickel ions, cobalt ions, tin ions, copper ions, lead ions, cadmiumions, etc., especially aluminum ions. See JP H06-254319A by Tokuda, etal., to TOYOBO Co., Ltd., published on Sep. 13, 1994 hereby incorporatedby reference in its entirety.

In an embodiment herein, the charge-enhancing additive is selected fromthe group of triphenylmethanes; ammonium compounds and immoniumcompounds; intensely fluorinated ammonium and immonium compounds;biscationic acid amide and acid imide derivatives; polymeric ammoniumcompounds; diallylammonium compounds; arylsulfide compounds; phenoliccompounds (respectively compounds of the CAS-No, 41481-66-7 and13288-70-5); phosphonium compounds; highly fluorine-substitutedphosphonium compounds; calix(n)arene compounds; metal complex compoundslike chromium-, cobalt-, iron-, zinc- or aluminum azocomplexes orchromium-, cobalt-, iron-, zinc- or aluminum salicyclic acid complexes(such as described by CAS-Numbers 31714-55-3, 104815-18-1, 84179-68-8,110941-75-8, 32517-36-5, 38833-00-00, 95692-86-7, 85414-43-3,136709-14-3, 135534-82-6, 135534-81-5, 127800-82-2, 114803-10-0,114803-08-6 and the like); benzimidazolon compounds; and/or azines ofthe following Color Index numbers, C. I Solvent Black 5, 5:1, 5:2, 7,31, 50; C.I. Pigment Black 1, C, I. Basic Red 2 and C. I. Basic Black 1and 2. See, EP 623941A2 to Groh, et al., published on Mar. 5, 1994,assigned to Hoechst Celanese Corp., hereby incorporated by reference inits entirety.

In an embodiment herein, the charge-enhancing additive contains anarylamino-substituted benzoic acid and/or an arylamino-substitutedbenzoic acid salt. The salts useful herein may be metal-containing saltsand may be salts of monovalent, divalent or trivalent metals.Alternatively, the charge-enhancing additive useful herein may containphenolate salts; or triazine phenol salts; or a triazine phenolate anionand a metal cation. See US 2016/0067717 A1 by Schultz, et al., to 3MInnovative Properties Co., published on Mar. 10, 2016; and US2019/0336896 A1 by Schultz, et al., to 3M Innovative Properties Co.,published on Nov. 7, 2019, all of which are hereby incorporated byreference in their entireties.

The charge-enhancing additive may be present in any suitable level asknown in the art; or in an amount up to about 10%; or from about 0.02%to about 5%, by weight of the polymer component.

Fillers useful herein are typically particulate materials added into thepolymer component to provide bulk and to reduce the overall materialcost and are extruded together. The particles are typically from about0.5μ to 5μ in diameter; although they may not have a regular shape.Non-limiting examples of fillers useful herein include inorganic fillerssuch as calcium carbonate, titanium dioxide, talc, barium carbonate,magnesium carbonate, magnesium sulfate, mica, clays, kaolin,diatomaceous earth, and the like. Organic fillers include chitin, carbonblack, wood and cellulose powders, etc.

In an embodiment herein, a pigment, whether liquid, solid, etc., may beadded to any of the fibers herein to provide a color to the fiber.

Without intending to be limited by theory it is believed that once thesplittable fibers herein are split into split fibers, and furtherprovided with an el caret charge, the fitter material's MERV (MinimumEfficiency Reporting Values) rating will very likely increase,indicating that the filter is better at removing particulates,especially charged particulates. See, for example,https://www.epa.gov/indoor-air-quality-iaq/what-merv-rating-1, herebyincorporated by reference in its entirety, which explains MERV ratingsand that it is derived from the American Society of Heating,Refrigerating, and Air Conditioning Engineers (ASHRAE) [seewww.ashrae.org].

In an embodiment herein the splittable fiber, the split fiber, themulticomponent fiber, the multicomponent staple fiber, and/or thenonwoven fabric is formed into a filter, such as an air filter forremoving particulates from the air; or a face mask; or a HEPA filter; ora filter having a MERV rating of at least 8; or a filter having a MERVrating of at least 10; or a filter having a MERV rating of at least 14;or a filter having a MERV rating to at least 16.

In an embodiment herein, the splittable fiber, the split fiber, themulticomponent fiber, the multicomponent staple fiber, and/or thenonwoven fabric is formed into a filter; or an air filter; or a vehicleair filter; or an automotive engine air filter, an automotive cabin airfilter, an HVAC air filter, a face mask/respirator filter; and acombination thereof; or a cigarette filter. In an embodiment herein, thesplittable fiber, the split fiber, the multicomponent fiber, themulticomponent staple fiber, and/or the nonwoven fabric is formed intoan insulator; or a heat insulator; or a sound insulator; or a thermalinsulator. In an embodiment herein, the splittable fiber, the splitfiber, the multicomponent staple fiber, and/or the multicomponent fiberis included or formed into a spun yarn. In an embodiment herein, thesplittable fiber, the split fiber, the multicomponent fiber, themulticomponent staple fiber, and/or the nonwoven fabric is included in awipe.

Testing Procedures and Equipment:

The TSI 8130A automated filter tester (see:https://www.tsi.com/products/filter-testers/automated-filter-tester-8130a/by TSI Incorporated, Shoreview, Minn., USA) can be used to test thefiltration efficiency herein. The TSI 8130A creates 0.3μ particles whichare injected into an airstream and passed through a filter sample. See:https://youtu.be/HSngoNqKXvI, which shows how the filter tester works.The 0.3μ particles are measured both upstream and downstream of thefilter sample. As charge (or lack thereof) greatly impacts such smallparticles, it this device and the associated test can easily showwhether the filter sample has an electret charge and/or show itsefficiency as measured in % penetration. The % penetration is calculatedas: (downstream particle concentration)/(upstream particleconcentration)×100.

A high % penetration indicates low filtration efficiency—i.e., manyparticles are passing through the filter. Conversely, a low penetrationindicates a high filtration efficiency where many particles are caughtand held by the filter. As the particles build up on the filter sample,the filter tester continuously monitors the flow rate and the resultingpressure drop across the filter.

All MERV tests herein are conducted according to ASHRAE MERV Standard52.2-2017 from the American Society of Heating, Refrigerating andAir-Conditioning Engineers (ASHRAE), hereby incorporated by reference inits entirety, available from the ASHRAE website at:https://ashrae.iwrapper.com/ASHRAE_PREVIEW_ONLY_STANDARDS/STD_52.2_2017.

The TOPAS Flat Sheet Filter Media Test System (Model #AFC132; “TOPAS”)quickly tests small discs of filter media according to the ASHRAEStandard 52.2-2017, hereby incorporated by reference in its entirety.TOPAS has proprietary software that creates potassium chloride particlesfrom 0.3 microns to 10.0 microns in diameter. The horizontal duct holdsthe sample and challenges the media per the ASHRAE Standard 52.2-2017 atthe filter design velocity (Residential furnace filters are 110 fpm).Upstream and downstream particle counters determine the size and numberof particles which are trapped and pass through the media giving eachparticle range (E1 0.3-1 micron, E2 1.0-3 micron, E3 3.0-10 micron) andcorrelating the efficiency in each group with the ASHRAE Standard 52.2.MERV rating chart.

Although flat sheet accuracy is reasonably close to that of a pleatedfilter, the dynamics of air flow, size of actual filter, pleat geometryetc. can have small effects on the filter performance vs. a flat sheet.See below comparison of flat sheet data to outside test lab of fullfilter. Resistance is nearly doubled due to this filter being a wireback design where the wire holds the pleat form but also adds resistancebecause of the blind area of the metal mesh. The filter frame alsoreduces the available media exposed to flow causing the TOPAS design toresult in a slightly higher velocity than the flat sheet test perASHRAE. Standard 52.2:

Sample IR (in Velocity Description w.g.) E1 E2 E3 MERV fpm Flat sheet0.20 32.2 65.5 91.3 11 110 Filter 0.40 21.8 71 93 11 113 IR = Initialresistance in w.g. = inches water gauge fpm = feet per minute (1 fpm =1828.8 cm/min)

Calculating the Area of a Pleated Filter: Pleated Volumetric Pleat PleatPleated area Air Flow Media Media Width height Length area (inVolumetric Rate Velocity Velocity in (in Please (in (in sq. square airflow (in cubic (in (in inches inches) count feet) inches) feet) (in CFM)meters/hour) feet/min) cm/sec) 23.75 0.9 35 5.51 1571.06 10.91 19683343.65 180.38 91.63 23.75 1.75 29 8.88 2531.16 17.58 1968 3313.65111.96 56.88

The SUMO-ION Electrostatic Fieldmeter (specifically model #MX-003) is acommercially-available (see: https://www.simco-ion.com/) fieldmeterwhich measures the static charge of a material such as a fiber, anonwoven fabric, etc.

In an embodiment herein, the split distribution of the splittable fiber(and/or the multicomponent splittable fiber, the multicomponentsplittable staple fiber, the nonwoven fabric, etc.) is determined with aBraunauer-Emmett-Teller (BET) test (see, for example,https://en.wikipedia.org/wiki/BET_theory) according to ISO 9277:2010“Determination of the specific surface area of solids by gasabsorption—BET method” (see, https://www.iso.org/standard/44941.html),hereby incorporated by reference in its entirety. The BET test measuresthe physical absorption of gas molecules onto the fiber (or sub-fiber)surface and therefore an increase in the BET test indicates an increasein surface area which corresponds to a higher split distribution/moresplitting of the splittable fiber into sub-fibers as compared to asample which does not contain split fibers.

That being said, it is recognized that the BET test only measures thetotal surface area (increase) and does not specifically distinguishbetween, for example, a single fiber which is split entirely intosub-fibers, and a plurality of fibers that are split only once to givethe same total surface area.

In an embodiment herein, the splittable fiber; or the multicomponentsplittable fiber; or the multicomponent splittable staple fiber; or thenonwoven fabric, herein possess a surface area after splitting; or aftercarding; of from about 115% to about 800%; or from about 125% to about700%; or from about 135% to about 650%; or from about 150% to about 600%of the surface area of a comparable sample; or of substantially the samesample; before splitting; or carding. In an embodiment wherein thesplittable fiber constitutes about 50% of the total fiber mass, then thesplittable fiber; or the multicomponent splittable fiber; or themulticomponent splittable staple fiber; or the nonwoven fabric, hereinpossess a surface area after splitting; or after carding, of from about115% to about 400%; or from about 125% to about 350%; or from about 135%to about 325%; or from about 150% to about 300% of the surface area of acomparable sample; or of substantially the same sample, beforesplitting; or carding.

In an embodiment herein, the split distribution of the splittable fiber(and/or the multicomponent splittable fiber, the multicomponentsplittable staple fiber, the nonwoven fabric, etc.) is determined with aMicronaire test (MIC) which is a Cotton industry standard measurement ofa sample's air permeability and is used as an indication of fiberfineness and maturity (seehttps://barnhardtcotton.net/blog/what-is-a-micronaire-in-cotton-and-why-does-it-matter/and also https://www.cotton.org/journal/2005-09/2/upload/jcs09-081.pdf),all hereby incorporated by reference in their entireties. The MIC may bemeasured via, for example, the Uster® HVI 1000(https://www.uster.com/en/instruments/cotton-classing/uster-hvi-2/),available from Uster Technologies AG, Sonnenbergstrasse 10, CH-8610Uster, Switzerland. When comparing a sample containing unsplit fiberswith a sample containing split fibers, the sample containing splitfibers should have a higher air resistance. Thus, for a single (orotherwise substantially identical) sample, measuring the MIC before andafter splitting (for example, before and after carding) would indicatewhether or not the splittable fiber(s) have actually split, and providean indication of the split distribution.

The scaling of a Micronaire instrument is by gauging known fiber sizesover a range of 0.2 denier (100% opened fibers) to 3 denier (100%un-opened fibers). The scale is accentually aligned with known fibersizes across the expected range of opening to determine a 0%-100% scale.Once the scale is established, then a nonwoven fabric sample containingsplittable fibers having an original known denier can be tested bothbefore and after splitting to determine the split distribution.

In an embodiment herein, the split distribution of the splittable fiber(and/or the multicomponent splittable fiber, the multicomponentsplittable staple fiber, the nonwoven fabric, etc.) is determined viavisual and/or computer analysis of, for example, one or more scanningelectron micrographs (SEMs). In such a method, identical; orsubstantially identical, samples may be compared before and after thesplitting step (for example, by carding), to determine the splitdistribution.

In an embodiment herein, the split distribution is characterized byanalyzing scanning electron micrographs (SEMs) to estimate and/orcalculate the split distribution. SEMs may also be used herein toestimate/calculate the increase in surface area after splitting; orcarding. It is recognized herein that counting microfibers andsub-fibers in a SEM image has one advantage over counting them in across section image, in that there is no ambiguity introduced bysplitting that might occur in cutting the fiber for the cross sectionimage. However, the cross section image also has an advantage over theSEM, which is that in the cross section image there is no uncertaintywhether a microfiber comprises one, two, or three segments, or 7, or 9segments, etc. In an SEM image, even discerning between fibers thatmight comprise 3, 4, or 5 segments from those that might contain 6, 7,or 8 segments, for instance, is also a difficult judgment call. For thisreason, counting the split and unsplit fibers in a cross section imageis more reliable than counting fibers in an SEM image.

Example 1

Control media is formed from 100% 3 dpf (denier per fiber) fibers.Splittable fibers according to the invention of the same (initial) sizeare formed into a nonwoven web and then split into a nonwoven fabriccontaining split fibers. This nonwoven fabric is formed into acomparable filter, and then charged and left uncharged. All threestructures are the same. The MERV test is conducted according to ASHRAEMERV Standard 52.2-2017 and the data recorded below.

Sample BW Thickness Air Perm IR IR Velocity Description (gsy) (mils)(CFM) (PA) (in w.g.) E1 E2 E3 MERV fpm Control 98.1 48.6 280.4 40 0.16−0.6 26.6 79.9 8 110 Uncharged 99.2 43.6 167.6 82 0.33 16.9 56.3 85.4 10110 Split fibers Charged Split 99.2 43.6 167.6 73 0.29 59.8 82.1 95.6 12110 fibers BW = basis weight gsy = grams per square yard [1 gsy × 1.196= GSM (grams per square meter)] Air perm = air permeability CFM = cubicfeet per minute as measured by Frazier Precision Instrument per ASTMD737 (1 CFM = 28.32 liters per minute) IR = Initial resistance PA =Pascals in w.g. = inches water gauge fpm = feet per minute (1 fpm =30.48 cm/min)

From the above it can be seen that the uncharged split fiber sampleincreases in efficiency for E1, E2 and E3 as compared to the controlsample. The charged split fiber sample increases in efficiency E1, E2,and E3 with respect to both the control sample and the uncharged splitfiber sample. The control sample achieves a rating of MERV 8, while theuncharged split fiber sample achieves a rating of MERV 10, and thecharged split fiber sample achieves a rating of MERV 12. In addition,the lower CFM of the split fiber samples also indicates an increasedsurface area compared to the control due to fibers due to the splitting.

Example 2

A commercially available nano fiber-based media from Next Nano (ProductNumber NP048. Web Address: https://nxtnano.com/products/hvac/) ispurchased. Nano fiber-based filtration media are typically fibers lessthan 200 nano meters (Tim) in diameter and are not typically charged.The pure physical filtration (through sieving) does not allow for depthfiltration and larger particles can build up on the surface of the mediacausing premature high resistance. Nano fiber-based filtration media arealso to be used for a typical residential furnace filter. Below is aninternal flat sheet test of such media compared to the invention whichuses depth filtration, physical filtration and electro statics tobalance the filtration media allowing adequate filtration.

Sample IR (in Velocity Velocity w.g) E1 E2 E3 MERV fpm m³/hr Next 0.2645.0 78.8 97.1 12 110 35.4 Nano Invention 0.29 59.8 82.1 95.6 12 11035.4 IR = Initial resistance in w.g. = inches water gauge fpm = feet perminute (1 fpm = 30.48 cm/min)

As can be seen the present invention provides similar measurements asthe Next Nano sheet; however, in a different technical manner.

Example 3

In an embodiment herein, nonwoven fabric samples with various splitdistributions are compared.

Control Sample is a nonwoven fabric containing 100% nonsplittable fibers(3 dpf) is measured by the BET test, and compared to Samples 1-3. TheControl Sample is not carded.

Sample 1 contains, by weight, 50% nonsplittable fibers and 50%splittable fibers. Both the splittable fibers and the nonsplittablefibers are initially of the same denier (3 dpf) as the control sampleand thus the fabric sample (prior to splitting) is essentially identicalto the Control Sample. Sample 1 is then “slightly” carded in order tosplit the splittable fibers into sub-fibers.

Sample 2 is essentially identical to Sample 1, except that Sample 2 is“normally” carded to split the splittable fibers into sub-fibers.

Sample 3 is essentially identical to Sample 2, except that Sample 3contains a charge-enhancing additive is added to the splittable fiberand Sample 3 is charged via Corona Charging. Without intending to belimited by theory it is believed that the significant increase insurface area between Sample 3 and Sample 2 is due to the charged fibersrepelling each other and thereby increasing the overall surface area.

The BET test results for these samples are show in the table below.

BET test surface area measurement Surface area after (square meterssurface carding (as Sample area/gram of sample) % of Control) ControlSample 0.145 100 Sample 1 0.209 144 Sample 2 0.267 184 Sample 3 0.303209

Accordingly, it can be seen that carding significantly increases thesurface area of the samples according to the present invention with asurface are ranging from 144% to 209% of the Control Sample which issubstantially the same as the Samples before splitting.

Example 4

In an embodiment of the present invention a conventional charge isapplied to the formed nonwoven fabric after a thermal bonding process.The charge polarity is negative 30 Kv @ 2.5 mA but can range from 0.5 KV@ 1 mA to 50 Kv @ 3.0 mA. A SIMCO-ION FMX-003 Electrostatic Fieldmeteris used to measure the charge after the formation to the nonwoven fabricand before electret charging. The same electrostatic fieldmeter is usedto measure the charge after electret charging and the results are shownbelow.

Sample Charge (in kV) Nonwoven fabric before charging 0.0 Nonwoven webafter charging −7.7 kV

Charge retention is a function of applied voltage, dwell time under theapplicator bar (i.e., line speed in a continuous process), fiber density(surface area and basis weight), base fiber polymer, charge-enhancingadditives and atmospheric conditions.

It should be understood that the above only illustrates and describesexamples whereby the present invention may be carried out, and thatmodifications and/or alterations may be made thereto without departingfrom the spirit of the invention.

It should also be understood that certain features of the invention,which are; for clarity, described in the context of separateembodiments, may also be provided in combination in a single embodiment.Conversely, various features of the invention which are, for brevity,described in the context of a single embodiment, may also be providedseparately, or in any suitable subcombination.

All references specifically cited herein are hereby specificallyincorporated by reference in their entireties. However, the citation orincorporation of such a reference is not necessarily an admission as toits appropriateness, citability, and/or availability as prior artto/against the present invention.

1) A process for forming a splittable fiber comprising the steps of: A)providing a multicomponent fiber; or a multicomponent staple fiber,comprising: i) a first thermoplastic segment comprising polymercomponent A; and ii) a second thermoplastic segment comprising polymercomponent B; B) providing a finish material, wherein the finish materialhas an evaporation point of less than about 160° C.; and C) at leastpartially coating the multicomponent fiber; or a multicomponent staplefiber with the finish material to form a splittable fiber. 2) Theprocess for forming a splittable fiber according to claim 1, furthercomprising the steps of removing the finish material from the splittablefiber after the fiber is split. 3) The process The method for forming asplittable fiber according to claim 1, wherein the finish materialcomprises a lubricant; or wherein the lubricant is selected from thegroup consisting of a plant-based oil, a natural oil, a synthetic oil, awater-soluble lubricant, and a combination thereof; or a vegetable oil,a mineral oil and a combination thereof; or a light vegetable oil, alight mineral oil, and a combination thereof; or a coconut oil, a cornoil, and a combination thereof. 4) The process for forming a splittablefiber according to claim 1, wherein when the splittable fiber is fullysplit into a plurality of sub-fibers, the sub fiber has a linear densityof less than about 5 denier; or less than about 2 denier; or less thanabout 1 denier; or less than about 0.8 denier; or less than about 0.4denier. 5) The process for forming a splittable fiber according to claim1, wherein the coating step is selected from the group consisting ofspraying the finish material onto the multicomponent fiber, immersingthe multicomponent staple fiber in the finish material, contacting thefiber and a film of liquid finish material on the surface of a transferroll, contacting the fiber with a bead of the finish material as thefiber passes through a grooved applicator, and a combination thereof; ora kiss-roll application process, a metered-finish application process,and a combination thereof. 6) (canceled) 7) A process for forming asplit fiber comprising the steps of: A) providing a splittable fiberproduced according to the process of claim 1; and B) splitting thesplittable fiber in a carding process to form a split fiber. 8) Theprocess for forming a split fiber according to claim 7, wherein theprocess does not employ a hydroentangling process. 9) The process forforming a split fiber according to claim 7, further comprising the stepof electret charging the split fiber; or wherein the electret chargingcomprises a process selected from the group of corona charging,atmospheric plasma deposition, and a combination thereof; or wherein theelectret charging comprises corona charging and atmospheric plasmadeposition. 10) (canceled) 11) A process for forming a nonwoven fabriccomprising the steps of: A) providing a splittable fiber by the stepsof: i) providing a multicomponent fiber; or a multicomponent staplefiber, comprising: a) a first thermoplastic segment comprising polymercomponent A; and b) a second thermoplastic segment comprising polymercomponent B; ii) providing a finish material; or providing a finishmaterial wherein the finish material has an evaporation point of lessthan 160° C.; and iii) at least partially coating the multicomponentstaple fiber with the finish material; and B) forming the splittablefiber into a nonwoven fabric. 12) The process for forming a nonwovenfabric according to claim 11, further comprising the step of: providinga nonsplittable fiber, wherein the forming step comprises forming thenonwoven web from the splittable fiber and the nonsplittable fiber. 13)The process for forming a nonwoven fabric according to claim 11, furthercomprising the step of removing, by weight, at least a portion of thefinish material; or from about 50% to about 100% of the finish material;or from about 75% to about 100% of the finish material; or form about80% to about 100% of the finish material. 14) (canceled) 15) The processfor forming a nonwoven fabric according to claim 11, further comprisingthe step of: electret charging a thermoplastic component selected fromthe group consisting of the first thermoplastic component, the secondthermoplastic component, and a combination thereof; or wherein theelectret charging comprises a process selected from the group of coronacharging, atmospheric plasma deposition, and a combination thereof; orwherein the electret charging comprises corona charging and atmosphericplasma deposition. 16) The process for forming a nonwoven fabricaccording to claim 11, wherein the forming step is selected from thegroup consisting of carding, thermal bonding, needle punching,spunbonding/spinbonding, air laying, hydroentanglement, melt blowing,hydro pulping, refining, wet laying, thorough air oven, cross-lapping,and a combination thereof; or thermal bonding, needle punching,hydropulping, wet-laying, chemical bonding, melt blowing, air laying,carding, needling, hydroentanglement, and a combination thereof; orthermal bonding, needle punching, hydropulping, wet laying, andcombination thereof. 17) The process for forming a nonwoven fabricaccording to claim 11, further comprising the step of splitting themulticomponent staple fiber into a split fiber. 18) (canceled) 19) Anonwoven fabric produced according to the process of claim 11, furthercomprising an additional nonsplittable fiber; or an additionalnonsplittable fiber having a linear density of from about 1 denier toabout 20 denier. 20) (canceled) 21) (canceled) 22) (canceled) 23) Thenonwoven fabric according to claim 11, further comprising acharge-enhancing additive. 24) A split multicomponent fiber comprising adurable charge. 25) The split multicomponent fiber according to claim24, wherein the durable charge lasts for at least about 1 year; or atleast about 2 years; or at least about 3 years. 26) (canceled) 27) Thesplit multicomponent fiber according to claim 24, further comprising acharge-enhancing additive. 28) A nonwoven fabric comprising the splitmulticomponent fiber according to claim 24, further comprising anonsplittable fiber. 29) (canceled) 30) (canceled) 31) (canceled)